517 research outputs found
Comparison of the simulation and experimental fatigue crack behaviors in the aluminum alloy HS6061-T6
AbstractThis work deals with rotating bending fatigue tests on aluminum alloy HS6061-T6. Results have been obtained for two sizes of narrow section diameter for specimens with one hole. Results show that fatigue endurance is reduced in the case of the hole. In order to explain this behavior, numerical analysis by FEM were carried out to determine the stress concentrations for the two types of specimens. It is found that the important factor affects fatigue life is the narrow section diameter of the specimens, and the maximum damage occurs in the outer part of the specimen at the first stages of loading, however, it moves toward the center of the bar under uniaxial loading. The number of cycles to failure predicted numerically is higher than the experimental one. This difference is attributed mainly to an upper stage of fatigue crack growth, particularly, the interaction between fatigue crack growth and growth that can not be accounted for in the numerical model
Global identification of electrical and mechanical parameters in PMSM drive based on dynamic self-learning PSO
A global parameter estimation method for a PMSM drive system is proposed, where the electrical parameters, mechanical parameters and voltage-source-inverter (VSI) nonlinearity are regarded as a whole and parameter estimation is formulated as a single parameter optimization model. A dynamic learning estimator is proposed for tracking the electrical parameters, mechanical parameters and VSI of PMSM drive by using dynamic self learning particle swarm optimization (DSLPSO). In DSLPSO, a novel movement modification equation with dynamic exemplar learning strategy is designed to ensure its diversity and achieve a reasonable tradeoff between the exploitation and exploration during the search process. Moreover, a nonlinear multi-scale based interactive learning operator is introduced for accelerating the convergence speed of the Pbest particles; meanwhile a dynamic opposition-based learning (OBL) strategy is designed to facilitate the gBest particle to explore a potentially better region. The proposed algorithm is applied to parameter estimation for a PMSM drive system. The results show that the proposed method has better performance in tracking the variation of electrical parameters, and estimating the immeasurable mechanical parameters and the VSI disturbance voltage simultaneously
The newly observed open-charm states in quark model
Comparing the measured properties of the newly observed open-charm states
D(2550), D(2600), D(2750), D(2760), D_{s1}(2710), D_{sJ}(2860), and
D_{sJ}(3040) with our predicted spectroscopy and strong decays in a constituent
quark model, we find that: (1) the D(2\,^1S_0) assignment to D(2550) remains
open for its too broad width determined by experiment; (2) the D(2600) and
can be identified as the 2\,^3S_1-1\,^3D_1 mixtures; (3) if
the D(2760) and D(2750) are indeed the same resonance, they would be the
D(1\,^3D_3); otherwise, they could be assigned as the D(1\,^3D_3) and
, respectively; (4) the could be either the
's partner or the D_s(1\,^3D_3); and (5) both the
and interpretations for the seem likely. The
and radiative decays of these sates are also studied. Further
experimental efforts are needed to test the present quarkonium assignments for
these new open-charm states.Comment: 26 pages,7 figures, journal versio
The littlest Higgs model and Higgs boson associated production with top quark pair at high energy linear collider
In the parameter space allowed by the electroweak precision measurement data,
we consider the contributions of the new particles predicted by the littlest
Higgs() model to the Higgs boson associated production with top quark pair
in the future high energy linear collider(). We find that the
contributions mainly come from the new gauge bosons and . For
reasonable values of the free parameters, the absolute value of the relative
correction parameter can be significanly large,
which might be observed in the future experiment with .Comment: latex files, 13 pages, 3 figure
Effects of Dietary Tryptophan Supplementation and Feed Restriction on Growth Performance and Carcass Characteristics of Goslings
Transition Form Factor up to within the Factorization Approach
In the paper, we apply the factorization approach to deal with the
transition form factor in the large recoil
regions. The B-meson wave functions and that include the
three-particle Fock states' contributions are adopted to give a consistent PQCD
analysis of the form factor up to . It has been found that
both the wave functions and can give sizable
contributions to the form factor and should be kept for a better understanding
of the meson decays. Then the contributions from different twist structures
of the kaon wavefunction are discussed, including the -breaking
effects. A sizable contribution from the twist-3 wave function is
found, whose model dependence is discussed by taking two group of parameters
that are determined by different distribution amplitude moments obtained in the
literature. It is also shown that and
, which are more
reasonable and consistent with the light-cone sum rule results in the large
recoil regions.Comment: 22 pages and 6 figure
Probing bulk viscous matter-dominated models with Gamma-ray bursts
In this paper we extend the range of consistency of a constant bulk viscosity
model to redshifts up to . In this model the dark sector of the
cosmic substratum is a viscous fluid with pressure , where
is the fluid-expansion scalar and is the coefficient of bulk
viscosity. Using the sample of 59 high-redshift GRBs reported by Wei (2010), we
calibrate GRBs at low redshifts with the Union 2 sample of SNe Ia, avoiding
then the circularity problem. Testing the constant bulk viscosity model with
GRBs we found the best fit for the viscosity parameter in the
range , being so consistent with previous probes; we also
determined the deceleration parameter and the redshift of transition to
accelerated expansion. Besides we present an updated analysis of the model with
CMB5-year data and CMB7-year data, as well as with the baryon acoustic peak
BAO. From the statistics with CMB it turns out that the model does not describe
in a feasible way the far far epoch of recombination of the universe, but is in
very good concordance for epochs as far as till present.Comment: 11 pages, 3 figures, submitted to JCA
QCD ghost f(T)-gravity model
Within the framework of modified teleparallel gravity, we reconstruct a f(T)
model corresponding to the QCD ghost dark energy scenario. For a spatially flat
FRW universe containing only the pressureless matter, we obtain the time
evolution of the torsion scalar T (or the Hubble parameter). Then, we calculate
the effective torsion equation of state parameter of the QCD ghost f(T)-gravity
model as well as the deceleration parameter of the universe. Furthermore, we
fit the model parameters by using the latest observational data including
SNeIa, CMB and BAO data. We also check the viability of our model using a
cosmographic analysis approach. Moreover, we investigate the validity of the
generalized second law (GSL) of gravitational thermodynamics for our model.
Finally, we point out the growth rate of matter density perturbation. We
conclude that in QCD ghost f(T)-gravity model, the universe begins a matter
dominated phase and approaches a de Sitter regime at late times, as expected.
Also this model is consistent with current data, passes the cosmographic test,
satisfies the GSL and fits the data of the growth factor well as the LCDM
model.Comment: 19 pages, 9 figures, 2 tables. arXiv admin note: substantial text
overlap with arXiv:1111.726
Measurements of the observed cross sections for exclusive light hadrons containing at , 3.650 and 3.6648 GeV
By analyzing the data sets of 17.3, 6.5 and 1.0 pb taken,
respectively, at , 3.650 and 3.6648 GeV with the BES-II
detector at the BEPC collider, we measure the observed cross sections for
, , ,
and at the three energy
points. Based on these cross sections we set the upper limits on the observed
cross sections and the branching fractions for decay into these
final states at 90% C.L..Comment: 7 pages, 2 figure
Partial wave analysis of J/\psi \to \gamma \phi \phi
Using events collected in the BESII detector, the
radiative decay is
studied. The invariant mass distribution exhibits a near-threshold
enhancement that peaks around 2.24 GeV/.
A partial wave analysis shows that the structure is dominated by a
state () with a mass of
GeV/ and a width of GeV/. The
product branching fraction is: .Comment: 11 pages, 4 figures. corrected proof for journa
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